proxy: overhaul backend error handling

Cleans up logic around response handling in general. Allows returning
server-sent error messages upstream for handling.

In general SERVER_ERROR means we can keep the connection to the backend.
The rest of the errors are protocol errors, and while some are perfectly
safe to whitelist, clients should not be causing those sorts of errors
and we should cycle the backend regardless.

1 files changed, 1 insertions, 0 deletions

diff --git a/proxy.h b/proxy.h
index 24a5ea0..87f2b7e 100644
--- a/proxy.h
+++ b/proxy.h
@@ -251,6 +251,7 @@ enum mcp_backend_states {
     mcp_backend_read_end, // looking for an "END" marker for GET
     mcp_backend_want_read, // read more data to complete command
     mcp_backend_next, // advance to the next IO
+    mcp_backend_next_close, // complete current request, then close socket
 };
 
 typedef struct mcp_backend_wrap_s mcp_backend_wrap_t;